The discussion of the background of the invention herein is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to was published, known or part of the common general knowledge at the priority date of any of the claims.
An optical lens is typically made of plastic or glass material and generally has two opposite surfaces which co-operate with one another to provide a required corrective prescription. When the positioning or shape of one of these surfaces with respect to the other is inaccurate, optical errors can be created.
Manufacturing of an optical lens to the required prescription requirements typically includes machining the surface of a semi-finished lens or lens blank. Typically, a semi-finished lens has a finished surface, for example the front surface and an unfinished surface, for example the back surface. By machining the back surface (also named “rear surface”) of the lens to remove material, the required shape and positioning of the back surface with respect to the front surface for the desired corrective prescription can be generated.
Optical lenses, and in particular ophthalmic lenses, require very high quality manufacturing process in order to obtain high quality optical lenses.
All ophthalmic lens manufacturing processes do not have the same quality, i.e. all the manufacturing processes are not capable of manufacturing a surface with the same accuracy.
In certain situation it may be very useful to have a method for checking beforehand the feasibility of an ophthalmic lens by an ophthalmic lens manufacturing process.
For example, when an eye care professional orders an ophthalmic lens to a lens provider, the lens provider needs to be sure that considering the manufacturing processes available, he is able to manufactured the ordered lens with sufficient optical quality.
When a lens designer works on a new lens design, it may be very useful to have a method for checking that the manufacturing processes at disposal have a sufficiently high quality to manufacture lenses with such new design.